The present invention relates to a twig branched cyclodextrin (branched dextrin branched cyclodextrin, hereinafter abbreviates as "BB-CD") and a method for the preparation thereof or, more particularly, to a BB-CD of which the branched portion is formed of a moiety of branched maltooligosaccharide and an efficient method for the preparation thereof.
Branched cyclodextrins have excellent and useful properties of, for example, high solubility in water so that investigations have been hitherto undertaken intensively for the development of the method for the preparation as well as utilization of such branched cyclodextrins. Several variations of branched cyclodextrins are known including those of which the branched portion is formed of a moiety of .alpha.-1,4glucan such as glucose, maltose and the like. These branched cyclodextrins are prepared enigmatically either by utilizing a specific enzyme having activity of synthesis of a branched cyclodextrin or by the enzymatic reaction in a mixture of cyclodextrin and an .alpha.-1,4-glucan such as maltose and maltotriose in the presence of a branch-splitting enzyme.
Branched cyclodextrins of which the branched portion is formed of a maltosyl or higher group are converted into a glucosyl cyclodextrin in the presence of glucoamylase or .alpha.-amylase since the branched portion is susceptible to the attack of these enzymes. Accordingly, it is eagerly desired to develop a branched cyclodextrin of which the branched portion is insusceptible to these enzymes.
It has been recently reported that panose can be used as the branched portion in the preparation of certain metal complexes having stability, and metals such as zinc, calcium and the like or ions thereof are expected to form a stable complex in the simultaneous presence of a branched dextrin such as panose and cyclodextrin. The complex formation of metals can be performed by the combined use of a branched dextrin and cyclodextrin but a alternative method is to use a BB-CD as a combination of a branched dextrin such as panose and cyclodextrin as a possibility. Such a cyclodextrin derivative, however, is not known in the prior art so that the above mentioned possibility seemed to be far from reality. Much less, no method has been reported for the preparation of such a cyclodextrin derivative.
For example, a method for the preparation of a branched cyclodextrin is known on the base of the discovery that maltosyl-and maltotriosyl-cyclodextrins are formed from cyclodextrin and maltose or maltotriose by utilizing the reverse reaction of a branch-splitting enzyme such as pullulanase. It is not known, however, that a BB-CD is formed from a branched dextrin and cyclodextrin by the reverse reaction of the branch-splitting enzyme.